Freighter
Characters who grew up as an apprentice under, assistant to, or who practiced the works of sailors & navigators of shallow waters, will have the chance to have this particular Extra Skill. For it pertains primarily to the knowledge of freighting small boats and rafts & how to navigate them through and around the currents, how to properly accelerate and when, and so forth. Thus while the character never has to be the one manning the boat or raft, they do need to have been exposed to the process for long periods of time. This time would need to be vastly longer if the character is learning on their own without a mentor.
With the knowledge and experience of a Freighter under their belt, characters with this skill can expertly identify strong and still currents, as well as signs of strong/still currents coming up, if the water is deep enough for the craft, sharp rocks or reefs under the water, and so forth. They can of course, also expertly appraise armor without any rolls, & properly determine the condition of the boat/raft. This could result in discovering that the boat or raft is flawed or rotten in some way, and thus subject to leaking water or easily broken, or vulnerable to rotting from water due to lack of oil protecting the craft, or if it's average but good quality, superior made with expertise allowing it to sustain more punishment, and so forth. In addition to all of this, should one with this skill spot any damage to the armor, so long as it isn't irreversable, they can repair the damage with the appropriate tools, materials and time to do so without any rolls (unless rushing the job).
Furthermore the character with this skill can navigate rapids better than most, granting them a +1 modifier to their boating proficiency. They can also adjust quickly to unfamiliar scenarios, receiving no penalties when boating, even when in the underdark. They have a greater than average chance to notice signs of more dangerous aquatic life such as monsters, giving them a +1 to Monster Lore check in regards to creatures dwelling in shallow water. Finally if someone with this skill is attempting to fashion together a raft, they and everyone aiding them in the project will get a +1 modifier to their check.
With the knowledge and experience of a Freighter under their belt, characters with this skill can expertly identify strong and still currents, as well as signs of strong/still currents coming up, if the water is deep enough for the craft, sharp rocks or reefs under the water, and so forth. They can of course, also expertly appraise armor without any rolls, & properly determine the condition of the boat/raft. This could result in discovering that the boat or raft is flawed or rotten in some way, and thus subject to leaking water or easily broken, or vulnerable to rotting from water due to lack of oil protecting the craft, or if it's average but good quality, superior made with expertise allowing it to sustain more punishment, and so forth. In addition to all of this, should one with this skill spot any damage to the armor, so long as it isn't irreversable, they can repair the damage with the appropriate tools, materials and time to do so without any rolls (unless rushing the job).
Furthermore the character with this skill can navigate rapids better than most, granting them a +1 modifier to their boating proficiency. They can also adjust quickly to unfamiliar scenarios, receiving no penalties when boating, even when in the underdark. They have a greater than average chance to notice signs of more dangerous aquatic life such as monsters, giving them a +1 to Monster Lore check in regards to creatures dwelling in shallow water. Finally if someone with this skill is attempting to fashion together a raft, they and everyone aiding them in the project will get a +1 modifier to their check.